Various methods have been developed to detect a target biomolecule in a specimen. Among them, a method using a nanopore is similar to a bio-pore system and has appealed to those skilled in the art as a high-sensitivity DNA detection system.
There are known various DNA detection systems using nanopores. One example of the detection systems is found in U.S. Pat. No. 6,015,714, which is entitled “characterization of individual polymer molecules based on monomer-interface interactions” and is intended to distinguish respective bases constituting DNA from each other using a very sensitive signal of a nanopore, thus performing DNA sequencing. According to the cited document, this has two pools, with a small pore being formed between the pools to permit DNA to enter one by one. After a DNA biopolymer is loaded on either of the pools, the passage of the biopolymer through the pore is measured, thus performing the DNA sequencing.
Further, U.S. Pat. No. 6,362,002, entitled “characterization of individual polymer molecules based on monomer-interface interactions”, discloses a method for making a nanopore to allow bases of a single stranded DNA to sequentially pass and determining a double stranded nucleic acid and a single stranded nucleic acid. Here, since the double stranded nucleic acid is untwisted in a single strand prior to passage, a long time is required.
Furthermore, U.S. Pat. Appl. Publication No. 2003/0104428, entitled “a method for characterization of nucleic acid molecules”, discloses technology that identifies a specific sequence using substances recognizing a specified local area of DNA, for example, protein or DNA and observes a signal variation caused by other substances bound to DNA so as to determine characteristics of a DNA sample using a nanopore, thus detecting a specific DNA sequence.
U.S. Pat. No. 6,428,959, entitled “methods of determining the presence of double stranded nucleic acids in a sample”, discloses a method that measures amplitude of current flowing through a nanopore while nucleic acids in a fluid specimen pass through the nanopore having a diameter of 3 nm to 6 nm, thus distinguishing a double stranded nucleic acid from a single stranded nucleic acid by current blockade.
However, the conventional DNA detection method and apparatus using the nanopore is problematic in that a diameter of the nanopore is large to deteriorate resolution where a required diameter of nanopore should be less than 10 nm, preferably 5 nm, so that the structure and detection conditions for the DNA detection apparatus are very complicated.
Until now, many efforts have been made to form a nanopore of a small diameter like a bio-pore. However, there are practically many problems because of manufacturing difficulties.